import java.util.Arrays;

public class Main {
    public static void main(String[] args) {
        int[]array={1,9,2,8,3,7,4,6,5};
        heapSort(array);
        System.out.println(Arrays.toString(array));
    }

    private static void heapSort(int[] array) {
        for (int parent = (array.length-1-1)/2;  parent >=0 ; parent--) {
            siftDown(array,parent,array.length);
        }
        int end = array.length-1;
        while(end>0){
            swap(array,0,end);
            siftDown(array,0,end);
            end--;
        }
    }

    private static void siftDown(int[] array, int parent, int end) {
        int child = parent*2+1;
        while (child<end){
            if(child+1<end&&array[child+1]>array[child]){
                child++;
            }
            if(array[child]>array[parent]){
                swap(array,parent,child);
                parent = child;
                child = parent*2+1;
            }else{
                break;
            }
        }
    }

    private static void swap(int[] array, int a, int b) {
        int tmp = array[a];
        array[a] = array[b];
        array[b] = tmp;
    }
}
